Association of genetic polymorphism with red blood cell alloimmunization in patients with sickle cell anemia

Red blood cell (RBC) alloimmunization is one of the serious complications associated with transfusion therapy in patients with sickle cell disease (SCD). The presence of the alloantibodies also hinders the provision of compatible blood for these patients and can lead to delayed hemolytic transfusion reactions (DHTR) and autoantibody formation. Most developed antibodies are directed to the Rh antigens. However, differences in the immune response of transfused patients who develop alloantibodies (responders) and who do not develop antibodies (non-responders) are not completely known. The hypothesis is that susceptibility to RBC alloimmunization is governed by many factors including genetic diversity among individuals. The aim of this study was to identify blood group alleles of 161 patients with SCD in chronic transfusion therapy (67 alloimmunized and 94 non-alloimmunized) and associations of polymorphisms on immunologically relevant genes (HLA genes and cytokines) with RBC alloimmunization. RBC genotyping was performed by microarray analysis with HEA BeadChipTM, RHD BeadChipTM and RHCE BeadChipTM (Immucor). Cytokine gene polymorphisms were analysed by PCR, PCR-RFLP and TaqMan genotyping assay (Applied Biosystems) while, HLA class II typing was performed using PCR-SSO (One Lambda). The Hardy-Weinberg equilibrium and the allelic and genotypic frequencies were obtained by Arlequin software. Allele and genotype frequencies were compared using the Fisher¿s exact test. The RBC antigen profile determination revealed that the C¿E¿, K¿, Fy(a¿), Jk(b¿), S¿ phenotype is prevalent. Also it was also found that 65% of patients with alloantibodies anti-Rh had Rh antigens variants which led to the development of clinically significant antibodies. Furthermore, analysis of cytokine gene polymorphisms revealed increased percentage of A allele and GA genotype of the TNFA¿308G/A in alloimmunized compared to non-alloimmunized patients (A allele: 16.4% vs 6.8%; P=0.004; GA genotype: 32.8% vs 11.7%; P=0.0021). Moreover, IL1B¿511T allele and IL1B¿511TT and CT genotype frequencies were significantly higher in alloimmunized than in non-alloimmunized patients (T allele: 53.0% vs 37.5%; P=0.0085; CT + TT genotypes: 81.82% vs 60.87%; P=0.0071). In relation to HLA class II, we found a higher frequency of HLA-DRB1*15 in alloimmunized patients to Rh antigens compared to non-alloimmunized (15.63% vs 6.98%; P=0.044). Results showed that TNFA, IL1B and HLA-DRB1 gene polymorphisms are associated with an increased risk of developing RBC antibodies in Brazilian patients with SCD. These findings can contribute, in the future, to improve transfusion and therapeutic strategies for patients with SCD (AU)